A method of removing solid paraffincontaining deposits from oil well surfaces and compositions therefor



United States Patent 3,342,264 A METHOD OF REMOVING SOLID PARAFFllN-CONTAINING DEPOSITS FROM OIL WELL SURFACES AND COMPQSITIONS THEREFORJohn W. Willard, Sr., Rapid City, S. Dak., assignor to J. B. OilTreatment Company, Incorporated, a corporation of South Dakota N0Drawing. Filed Aug. 12, 1965, Ser. No. 479,276 9 Claims. (Cl. 166-38)ABSTRACT OF THE DISCLOSURE Solid parafiin-containing deposits onsurfaces in oil wells are removed by introducing a treating compositioncontaining lecithin into the interior of the Well and into intimatecontact with the deposit, introducing an aqueous solution of alkali intothe Well, and thereafter flushing the well with water. In anothervarient, the well is treated with a composition which preferablycontains a water soluble alkali metal silicate, a miscelle-forming rosinacid soap, a partially saponified triglyceride vegetable oil, atriglyceride vegetable oil, alkali, a hydrocarbon solvent, a cyclicalcohol, lecithin and an alkaline earth metal silicate.

This application is a continuation-in-part of application Serial No.332,859, filed December 23, 196-3, now abandoned in the name of John W.Willard, Sr.

The present invention relates to methods of cleaning oil Wells and oilwells that also produce gas. The invention is concerned not only withthe cleaning of the metallic surfaces within the wells, but also thecleaning of the adjacent producing formations and the flow lines fromthe well to the storage tanks. The invention is also concerned with anovel cleaning composition that is especially useful for removing solidhydrocarbon-containing deposits from surfaces, a process for preparingthe novel cleaning composition, and a process for cleaning surfaces withthe composition.

In addition to the desired oil, or gas and oil, producing formationsalso yield to a well certain quantities of undesired materials. Amongthese are paraifins, asphaltic and waxy materials, and silt, sand, gums,minerals, salts and hydrates and other materials. These undesiredmaterials are a great source of trouble in Wells because they tend toclog the producing formation and reduce or shut oi the flow of the well.

In the past, the problem of removing parafiin deposits from pumpingwells and flow lines has been attacked in a number of ways. The oldestmethod, which was perhaps the most effective method heretofore, was toclean the well mechanically, e.g., by scraping. But this method resultedin lost production time and high labor costs and required special tools,all of which was often too expensive to be economically feasible.

It has also been a common practice to try to restore the flow of a wellby cleaning the well with chemical solvents. In order to do this, hotoil or solvent have been introduced in liquid phase into the well in aneffort to dissolve the undesired materials. In actuality, however, thesolvents used in the prior art have been effective only to dissolve theparafiins and other hydrocarbons that are readily soluble in organicmedia. Moreover, the use of such solvents has been a time-consuming andcostly operation and has resulted in considerable loss of productiontime. But perhaps worst of all, the prior art methods of cleaning wellsby the use of solvents such as hot oil or other solvents have beenlargely ineffective and in many instances have served only to worsen thefouling of the well. This is because when the praffin and otherrelatively readily soluble constituents of the sludge are removed bysolvent, the proportion of insoluble soil-like constituents of thesludge rises, with the result that the sludge becomes even denser andless permeable by gas and oil.

Accordingly, it is an object of the present invention to provide methodsfor cleaning wells and producing formations, characterized in that theconstituents of the fouling sludge are removed.

Another object of the present invention is the provision of methods forcleaning wells and producing formations, characterized in thatredeposition of sludge following cleaning is greatly inhibited.

Still another object of the present invention is the provision ofmethods for cleaning wells and producing formations which can beperformed in only a small fraction of the time previously consumed bycleaning operations.

It is also an object of the present invention to provide methods forcleaning oil wells and producing formations, which will cost only afraction of the cost of methods heretofore practiced for the samepurpose.

It is a further object of the present invention to provide methods forcleaning oil wells and producing formations, which will be relativelysimple and easy to practice with uniformly desirable results.

It is a further object to provide -a novel, highly effective cleaningcomposition for removing solid hydrocarboncontaining deposits fromsurfaces by the method of the invention.

It is a further object to provide a process for preparing.

with polyol esters of fatty acids, and thereafter contacting the sludgewith an aqueous solution of alkali metal hydroxide, after which the wellcan be flushed with Water.

In preferred embodiments of the invention, an alkali metal silicate isalso present in the cleaning composition, as is also a finely dividedprecipitate of polyvalent metal silicate, preferably divalent, morepreferably Group II elements having atomic numbers from 1256, e.g.,magnesium, calcium, zinc, strontium, cadmium or barium, and mostpreferably selected from the class consisting of calcium and magnesiumsilicates. Also in the preferred embodiments, the liquids are applied tothe Well at elevated temperature. It is also preferred that the polyolbe a glyceride. In certain preferred embodiments, lecithin is alsopresent in the cleaning composition. It is further preferred that theester be dissolved in a solvent comprising at least principallyaliphatic hydrocarbons having 10 12 carbon atoms. Another preferredrelationship is that the ester be only a partial ester.

As a result of operation according to any or all of the preferred formsof the invention, the ester penetrates and at least partially dissolvesthe paraffin of the sludge, whereupon the subsequent treatment withalkali metal hydroxide at least partially saponifies the esters to formwater soluble alkali metal soaps which complete the cleaning action,whereupon flushing with water removes the whole of the sludge, leavingclean surfaces. When lecithin is used, the polar portion of the lecithinmolecule migrates to the iron surfaces, and upon hydrolysis, the leci VU sludge. In addition, the alkali metal silicates remove grease andpeptize agglomerates and thus remove solid dirt.

In greater detail, the preferred forms of the invention are set forth asfollows:

Ester These vegetable oils are largely trigylcerides, and the fatty'acidmoiety is largely oleic, linoleic and linolenic. It is also preferred tomodify the esters of the present invention to regulatetheirhydrophile-lyophile balance.

This is preferably done by partial de-esterification of the polyol, forexample, by partial saponification with an alkaline earth metalhydroxide such as calcium hydroxide, to increase the proportion ofmonoand di-esters.

Ester solvent In order to increase the surface area of the ester andregulate viscosity, theester is applied to the well and its associatedproducing formation in a solvent, preferably 'a'hydrocarbon, and morepreferably primarily aliphatic hydrocarbons having 10-12 carbon atoms.When a slvent of such characteristics is employed, the cleaning actionis greatly augmented. This is quite unexpected, for it would of coursebe assumed that the shorter the hydrocarbon chain the greater thesolvent power and the greater the cleaning action. In fact, however, thepreferred solvents are considerably more effective than hydrocarbons ofshorter chain length such as the principal gasoline hydrocarbons.

In some instances, the medium of the cleaning agent will be entirelyorganic. In other cases, the organic medium will be dispersed in waterpreferably in the form of an emulsion. In general, the higher theproportion of parafiin the other organic-soluble components of thesludge, the greater will be the organic phase of the cleaningcomposition; while the higher the proportion of soillike components ofthe sludge the greater will be the aqueous phase of the cleaningcomposition.

Lecithin Commercial lecithin is a mixture of the diglycerides ofstearic, palmitic and oleic acids, linked to the choline ester ofphosphoric acid. Structurally, it appears as folin which R and R arehydrocarbon chain-s having 15-21 carbons and more than 50% 17 carbons,and R R and R are lower alkyl, e.g., methyl, ethyl, propyl or butyl,preferably methyl.

It will be seen that one portion of the molecule is lyophilic, while theother portion is polar and hence is attracted to the metal surfaceswithin the well. The paraffin will be penetrated by the organic phase ofthe cleaning composition with the result that the lecithin can migratereadily to the metal surface. Upon subsequent treatment with alkalimetal hydroxide and then water, the lecithin on the metal surface hasthe effect of dislodging scale at the surface, so that the scale breaksoff in relatively large chunks that have the imprint of the bare metalsurface on them. It may be that the saponification of hydrolysis of thelecithin causes the scale to break away, but it seems more probable thatthe scalebreaking action ofthe lecithin occurs as a result of swellingin water or the formation of a water-in-solid colloid, for thescale-breaking action of the lecithin is observed upon flushing withwater rather than upon prior treatment with alkali metal hydroxide. Thebare metal surface remains with at least the phosphate portion of the Ilecithin molecule adhered thereto, thereby to retard further scale orsludge formation on the metal surfaces- Silicate:

It is preferred to use substantial quantities of alkali metal silicatesin the cleaning composition, preferably sodium silicate. These silicatesremove large quantities of grease and also peptize aggl-omerates andthus removes solid dirt. In other words, the silicates help wet outindi-' vidual dirt particles and cause the line dirt particles to repeleach other and remain in suspension until flushed away, and alsoemulsify the oil and grease present in the sludge. In addition,solutions of water-soluble silicates have high specific heats and goodheat transfer properties and hence conduce to the rapid transfer of heatto the well structure and producing formation.

It has also been found that the cleaning action of the present inventionis greatly enhanced by the presence of small but effective amounts ofpolyvalent metal silicates, preferably divalent, preferably silicates ofGroup II metals having, atomic numbers between 12-56, e.g., magnesium,calcium, zinc, strontium, cadmium and barium. Particularly preferred aremagnesium and calcium. These polyvalent metal silicates can be formed insitu by contact between polyvalent metal salts dissolved in water andsodium silicate. If the water is hard to begin -wit-h and containssubstantial proportions of calcium and magnesium ions, then it isnecessary only to add the sodium silicate to the Water, whereuponsufficient calcium and magnesium silicate will form. Otherwise, it isdesirable to add water-soluble polyvalent metal salts to water prior toaddition of alkali metal silicates to the water, and prior to additionof the esters.

Therefore, it is preferred to prepare the cleaning composition of thepresent invention in two steps: (1) the polyvalent metal silicate isformed either with hard water or with the addition of polyvalent metalsalts to water and the reaction with alkali metal silicate, whereupon afinely divided colloidally suspended precipitate of the polyvalent metalsilicate is formed; and (2) thereafter, an aqueous emulsion with theester and ester solvent and other ingredients of the cleaningcomposition is formed.

When the composition of the present invention is inserted into a well toclean the well, the polyvalent metal silicates are strongly attracted tothe iron surfaces. After removal of the sludge, they remain behind onthe iron surfaces and inhibit subsequent deposition on the surfaces thusprotected.

Other ingredients Various other ingredients may also be used in order topromote the cleaning action of the present invention. Among these are asolution of sodium abietate or sodium resinate in a solvent such ascyclohexanol or methylcyclohexanol. This resinate emulsifies the oil andgrease present in the sludge, acts as a solvent for solid carbonaceousproduct and forms some methyl cyclohexanol abietate which has :goodsolvent and dispersing properties. Sodium resinate also renders thesilicates compatible with the alkaline earth metal salts and lecithinsolution if used. Sodium salts of fatty acids also can be used for thispurpose. Other useful ingredients are cold process laundry soap, sodaash, and other detergent or cleansing agents.

Temperature The use of heat with the process of the present inventionvaries with the type of sludge and the method of treatment. When anaqueous emulsion is used in contact with a sludge in which the paraffinis dispersed in small particles throughout the sludge, .a temperaturebelow the melting point of the paraflin is desirable so as to preventthe formation of a continuous organic phase in the slurry. On the otherhand, when a non-aqueous organic cleansing agent is used, then thehigher the temperature the better up to the limitations imposed by theboiling points of the various fluids. Also, when using an aqueousemulsion, it is of course desirable to operate below the boiling pointof water, preferably around 200 F. On the other hand, use of heat is notaltogether necessary and in many instances it is possible to operate atambient temperature.

Alkali After the cleaning composition has been in contact with the welland producing formation for a suitable period of time, an alkali metalhydroxide is placed in contact with the cleaner-saturated paraffindeposit of the well. The alkali metal hydroxide is preferably eithersodium or potassium, and sodium is preferred. It is introduced inaqueous solution. Preferably, it is introduced hot.

It is not necessary that the alkali metal hydroxide be introduced intothe well as such. It is possible to form it in situ, as by the use ofthe carbonates or silicates or bicarbonates or phosphates, which uponhydrolysis produce the hydroxide.

The alkali metal hydroxide, applied hot to the previously treatedsludge, partially saponifies the fatty acid glycerides or other estersand lecithin if any. In addition, this saponification introduces heatinto the well because the saponification is exotherimc. The resultingsodium salts are water-soluble soaps that act as dispersing andemulsifying agents.

Procedure As is well known, an oil well ordinarily comprises a verticalcylindrical casing in contact with the producing formation andmulti-perforate adjacent its lower end to permit the entry of oil fromthe producing formation into an annular space between the casing andconcentric internal tubing. A standing valve is disposed adjacent thelower end of the tubing and a traveling valve is vertically reciprocatedby rods that are also concentric within the tubing and casing. At theupper end of the assembly, the casing has a casing head and the tubinghas a stuffing box within which the rods slidab-ly reciprocate. Oilforced upwardly in the tubing by the traveling valve leaves the upperend of the tubing through a flow line. The casing head is also providedwith conduits for the exit of casing head gas and liquids from the upperend of the casing and also for the introduction of liquids into thecasing.

Also, ordinarily available in oil fields are trucks that are equipped totreat oil wells. These trucks carry tanks for transporting liquids and afurnace to heat the liquid. The trucks also ordinarily carry two pumps,operated from a power take-off from the truck drive, one pump being alow pressure pump and the other a high pressure pump. There is thusordinarily equipment available for practicing the process of the presentinvention.

After a sample of the sludge that fouls the well has been obtained andtested to determine its composition and therefore the best cleaningprocedure, the necessary liquids may be withdrawn as needed from thetruck. If the well is not so badly fouled that the pump can stilloperate, and also the sludge contains a high percentage of inorganicmatter, then the pump can be positioned so that both the traveling valveand the standing valve are open. Pressure in the casing and the tubingare thus equalized. A quantity of boiling water can then be pumped intothe tubing to displace the petroleum from the sludge area and to preheatthe sludge. The hot water is left in contact with the sludge for aperiod of time that depends on the thickness of paraffin accumulationand the bottom hole temperature of the well. The higher the temperaturethe shorter the contact time that is required.

The appropriate cleaning composition can then be pumped into the tubing.The cleaner is heavier than the previously introduced water and willdisplace the water and contact the fouled portion of the interior of thewell. Depending upon the hydrostatic pressure in the formation, thedisplaced Water will either rise in the casing or discharge into theformation.

After the cleaner has been in contact with the sludge for an appropriatetime, the caustic solution can be heated and pumped into the tubing,thereby forcing the cleaning solution ahead of it into the casing. Afterthe caustic solution has been in contact with the sludge for anappropriate time, hot water such as boiling water can be pumped into thetubing to flush the well and can be left in contact with the sludge foran appropriate time. The pump is then started and the water, with somecaustic and cleaner, is pumped out of the well. This mixture can eitherbe discharged into the flow line or recycled into the casing, asdesired.

One characteristic feature of operation according to the presentinvention is that not only does the flow promptly increase, but also itcontinues to increase over a protracted period of time after thetreatment has been completed. Apparently, this is because the cleaningsolution and the caustic solution are heavier than the oil and continueto penetrate the producing formation after treatment of the Well hasbeen completed, with the result that the well cleansing action of thepresent invention is still further augmented.

If the pump is plugged, then the first effort must be to open the pumpand allow the passage of fluid. A petroleum naphtha and water areadmixed to form an emulsion that is heated and pumped into the tubingand boiling water is pumped into the casing. The hot water causes thetubing to expand and also loosens the sludge. When the pump is againoperative, the previously described cleaning cycle can be followed.

If the sludge is mainly parafiin or is of the asphaltic parafiin type,then the initial treatment with hot water is not used. Instead, theremoval of hydrocarbonaceous material is effected with solvent which hasa substantially higher boiling point than water and therefore can beheated to a substantially higher temperature than water.

If the well has a high bottom oil pressure, then after the last orflushing step with hot water, oil from a storage tank at the well sitewill be pumped into the tubing using the hi h pressure pump on the truckto exert the necessary pressure to force the cleaning ingredients intothe formation.

When there is indication that the pay face of the formation has beenpartially plugged, it may also be necessary to wait a period of timesuch as a week after cleaning the well and then repeat the cleaningoperation.

The above described cleaning composition and method are'highly effectivefor the removal of solid hydrocarboncontaining deposits from oil wells,pumping equipment, flow lines and metallic or other surfaces in general.However, the method does require the further step of contacting theester-treated surface from which the deposit is to be removed with anaqueous solution of an alkali. It would therefore be desirable toeliminate the alkali treatment and provide a method in which only onesolution need be employed.

It has been further discovered that the treatment with the aqueousalkali may be eliminated by using the special cleaning composition ofthe invention. The composition may contain a water soluble metalsilicate, a water soluble micelle-forming soap such as an alkali metalrosin soap, and the partially saponified ester of a fatty acid and apolyol. Preferably, the composition also contains a vegetable oil suchas corn oil, and/or a water soluble compound providing an alkalinereaction such as alkali metal hydrorides and carbonates, and/ or ahydrocarbon solvent. An alcohol may be present, and preferably a cyclicalcohol such as cyclohexanol or mcthylcyclohexanol.

For best results, the cleaning composition should also contain analkaline earth metal silicate, and/ or a partially saponified productresulting from the reaction of an ester of a fatty acid and a polyolwith an alkaline earth metal hydroxide, and/ or lecithin. Thiscombination of ingredients, in addition to those previously recited,seems to have a synergistic effect and a cleaning composition isproduced which has unique cleaning ability even at low temperatures andat short contact periods.

The ingredients in the composition may be prepared in accordance withthe teachings appearing hereinbefore. However, better results areobtained when the composition is prepared by the preferred procedure ofthe invention and when employing the preferred ingredients.

For best results, the cleaning composition should be prepared from theingredients listed below:

Substance Broad Preferred Range Amount Alkali metal rosin soap (lbs) 2-2. 2 Alkali metal metasilicate pentahydrate (1bs.) 6-10 8 Refinedvegetable oil or corn oil (lbs). 2-3 2. 2 Alkali metal hydroxide (lbs)2-4 2 Vegetable oil or corn oil slurry (10 parts of corn oil partiallysaponified with one part of alkaline earth metal hydroxide in 4 parts ofwater, by weight) (lbs) 6-10 8. 6 Lecithin concentrate containing 65%soy bean phosphatides and 35% soy bean oil (lbs). 1-3 2 Petroleumnaphtha, containing largely aliphatic hydrocarbons having 1012 carbonatoms (gals) 3-6 4. 7 Cyclohexanol or methylcyclohexanol (lbs 2-6 4. 4Magnesium sulfate heptahydrate (grams) 20-100 21 Calcium chloride(anhydrous) (grams)- 10-50 10. 5 \Vater (gals) 6-10 8 It is understoodthat chemical equivalents of the above substances may be substitutedwhen desired, including those mentioned hereinbefore. Anhydroussubstances may be substituted for the hydrated substances, and viceVersa, in equivalent amounts. Suitable organic solvents for the rosinsoap may be substituted for the methylcyclohexanol or cyclohexanol, orhydrocarbon solvents in general for the petroleum naphtha. Additionally,other satisfactory water soluble alkaline earth metal salts may besubstituted for the magnesium sulfate or calcium chloride mentionedabove. Sodium or potassium hydroxide, metasilicate and rosin soap areusually preferred. The water should be present in an amount to providean aqueous medium for reaction of the above ingredients and have aninitial temperature of at least 60 C. and the cyclohexanol ormethylcyclohexanol should be present in an amount sufficient to dissolvethe rosin soap. The petroleum naphtha should be present in an amount toprovide a hydrocarbon medium for the lecithin concentrate.

When preparing the cleaning composition of the invention, preferably theabove ingredients are placed in a reaction vessel provided with heatingand stirring means, and then heated with stirring at a temperature of atleast 80 C., and preferably at 90100 C. The heating may continue untilthe ingredients, upon cooling, will set to a pasty mass, which isusually yellow in color. There is a definite reaction which takes placeduring this heating step, and this reaction is essential in producingthe universal cleaning composition of the invention. Shorter heatingperiods are required at higher temperature within the above range, andlonger periods at the lower temperatures. However, usually a heatingperiod of about /22 hours is sufficient, although longer or shorterperiods often may be used when desired provided the reaction noted aboveoccurs. Also, temperatures higher than 100 C. may be employed ininstances where the reaction vessel is under pressure.

' The universal cleaning composition concentrate prepared as describedabove is preferably diluted with an aqueous medium such as water. Forbest results, approximately one volume of the concentrate should beadded to four volumes of hot water in the field immediately prior toadding the cleaning composition to the oil well tubing or casing. Thetemperature of the Water should be at least and, for best results, aboutZOO-212 F. The aqueous medium containing the concentrate may be added tothe oil well tubing or casing as described hereinbefore.

It is not necessary to follow the cleaning solution treatment with analkali solution treatment; however, this may be done if desired. Thecleaning solution is very effective, and usually contact with the sludgefor 10-15 minutes is suflicient to loosen it. Much longer contactperiods may be employed, such as 1-3 to 1-12 hours, or longer asextended periods of contact do no harm. The cleaning solution treatmentis preferably followed by a water flush.

Experimental evidence indicates that the hot, dilute aqueous cleaningsolution is altered when it comes in contact with the sludge and oil inthe well, and the properties of the solution change drastically, Thealtered cleaning solution resulting from this contact has been found tobe very effective in dispersing and removing the sludge at temperaturesas low as -6570 F., or even lower. Thus, the universal cleaning solutionof the invention is unique in that when the hot solution comes incontact with a certain type of sludge, and the oil from which the sludgewas liberated, a different and even more effective cleaning solutionseems to be produced. This new cleaning solution will penetrate anddisperse the sludge more rapidly and at a lower temperature than theoriginal cleaning solution. The reason for these unusual and unexpectedresults is not fully known at the present time.

To enable those skilled in this art to practice the invention, thefollowing illustrative examples are given:

EXAMPLE I Thirteen pounds of hydrated sodium sesquisilicate is added to45 gallons of water and the mixture is heated to F. The water is hard"and contains about 300 par-ts per million of calcium and magnesium ion.A finely divided colloidally suspended precipitate of calcium andmagnesium silicate forms and lends a cloudy cast to the solution. Tothis hot liquid there is then added 39 pounds of a solution of one partby weight of sodium abietaterosin in two parts by weight ofmethylcyclohexanol. Then, 39 pounds of a slurry is added that isobtained by the partial saponification of a commercial grade corn oilwith calcium hydroxide in the ratio of one part by weight of calciumhydroxide to four parts by weight of water to ten parts by weight ofcorn oil. This slurry has previously been warmed until essentially allof the hydroxide has reacted. The slurry includes unreacted corn oil aswell as partially saponified corn oil. Finally, 39 pounds of a solutionis added which is lecithin concentrate in an amount of 10% by weight ina solvent. The lecithin concentrate is approximately 65% soy beanphosphatides and 35% soy bean oil and is sold commercially by theArcher-Daniel-Midland Company of Minneapolis, Minnesota under the brandname of R-Lecin TS. The solvent is a petroleum naphtha having a boilingrange of 355410 F., and an A.P.I. gravity of 46.3 and a closed cup flashpoint of 141 F., comprising principally aliphatic hydrocarbon having10-12 carbon atoms and sold by the Skelly Oil Company of Kansas City,Missouri, under the brand name of Skellysolve-T.

One hundred gallons of boiling water is pumped into the tubing and leftin contact with the sludge for 15 minutes. The suspension resulting fromthe admixture of these ingredients is then added, at a temperature of190 F. After 25 minutes an equal volume of 10% sodium hydroxide solutionat a temperature of 190 F. is pumped into the tubing and into contactwith the previously treated sludge. After another 25 minutes, 300gallons of boiling water are pumped into the tubing and left to stand 20minutes. The pump is then operated and most of the water and caustic andcleaning solution and sludge is removed from the well. Pieces of scalefrom adjacent the ferrous surfaces in the well bear the imprint of thesurfaces, indicating that the ferrous surfaces are clean and exposed.

EXAMPLE II A cleaning composition is made up with comprises 9 pounds ofa commercial cold process laundry soap having moisture and volatileingredients about 36%, anhydrous material both organic and inorganicabout 65%, and free caustic 0.10%; 13.5 pounds of melted rosin; 1.5gallons of corn oil; 1.0 gallon of methylcyclohexanol; 0.5 gallon of 40%Be aqueous sodium silicate solution; 1.5 gallon of Stoddard solvent; andpounds of sodium carbonate. The cold process soap is a mixture ofcoconut oil, castor oil and tallow saponified at a temperature below 80C. using caustic soda. The laundry soap is dissolved in 6 gallons of 200F. water. A solution of 13.5 pounds of rosin is dissolved in one gallonof methylcyclohexanol and then heated to 200 F. and added With stirringto the soap solution. The corn oil is then added with stirring, followedby the sodium silicate solution and the Stoddard solvent and finally thesodium carbonate is dissolved in the mixture. To apply this cleaningcomposition to the well, 35 gallons of the cleaning composition and 35gallons of Water are mixed together and heated to 200 F. and introducedinto the space between the polish rod and the walls of the tubing underpressure of 350 p.s.i. The solution remains in contact with the pump inthe well until the well is no longer fouled, as evidenced by the factthat the pump works freely. Next, 35 gallons of a 2% by weight sodiumhydroxide aqueous solution is heated to 200 F. and added to the casingthrough the annulus. Otherwise, the method of Example I is followed.

EXAMPLE III Example I is repeated, except that soft water is usedcontaining no measurable quantity of polyvalent metal ion, that is, nocalcium or magnesium.

EXAMPLE IV Example I is repeated, except that the solution of lecithinis omitted.

EXAMPLE V Example I is repeated, except that in place of the cleaningcomposition applied in the first step of Example I, there is used 49gallons of the naphtha of Example I containing dissolved in it 3 poundsof the lecithin concentrate of Example I.

EXAMPLE VI Example I is repeated, except that in place of the cleaningcomposition applied in the first step of Example I, there is used asolution of 5 gallons of corn oil in 45 gallons of the naphtha ofExample I.

In all of these examples, various degrees of good cleaning not only ofthe paraffin but also of the soil-type constituents of the sludge fromthe well and the producing formation is observed. In addition, in thecase of all examples except Examples 11 and VI, a substantialretardation of the re-deposition rate of sludge and scale is alsoobserved.

From a consideration of the foregoing disclosure, therefore, it will beevident that all of the initially recited objects of the presentinvention have been achieved.

Although the present invention has been described and illustrated inconnection with preferred embodiments, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit of the invention, as those skilled in this art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the present invention as defined by theappended claims.

EXAMPLE VII This example illustrates the preparation and use of theimproved cleaning composition of the present invention which does notrequire a treatment with an aqueous solution of alkali.

The following ingredients were placed in a reactor provided with heatingcoils and a stirrer:

8 gallons of water having a temperature of 60 C.

21 grams of magnesium sulfate heptahydrate 10.5 grams of calciumchloride (anhydrous) 8.0 lbs. of sodium metasilicate pentahydrate 2.0lbs. of sodium hydroxide 6.6 lbs. of sodium rosinate in cyclohexanolsolution (1 part by weight of sodium abietate-rosin in 2 parts by weightof cyclohexanol) 2.2 lbs. of refined corn oil 8.6 lbs. of a calcium cornoil slurry prepared as in Example I 2 lbs. of the lecithin concentrateemployed in Example I 4.65 gallons of the petroleum naphtha employed inExample I In preparing the composition, the hot water was added to thereaction vessel, followed by the water soluble inorganic compounds,which resulted in a finely divided colloidally suspended precipitate ofcalcium silicate and magnesium silicate. To this hot solution orsuspension was added with stirring the cyclohexanol solution of therosin soap, followed by the refined corn oil and calcium corn oilslurry. The calcium corn oil slurry was prepared as in Example I, i.e.,by partial saponification of a commercial grade of corn oil with calciumhydroxide in a ratio of 1 part by weight of calcium hydroxide to 4 partsby weight of water to 10 parts by weight of corn oil. The slurry waswarmed until essentially all of the calcium hydroxide had reacted, andincluded unreacted corn oil as well as partially saponified corn oil.Then, the lecithin concentrate was added in the form of a suspension inthe petroleum naphtha.

The above mixture was heated with stirring at C. and, when cooled, itformed a pasty yellow mass. Each volume of the cleaner concentrate thusprepared was diluted with 4 volumes of hot water heated to 200 F. andthe resulting cleaning solution was used in removing sludge from an oilwell.

The oil well was about 6,000 feet deep and had a 2 /2 inch tubing and ainch sucker rod, and contained about 20 barrels (42 gallons each) of oilin the tubing. The well was producing about 20 barrels of oil per dayand extensive sludge deposits had formed on the surfaces in contact withthe oil. Approximately gallons of the cleaning solution was pumped intothe tubing and left in contact with the sludge for about 3 hours. Thewell was then flushed with water.

The above treatment resulted in the removal of the sludge from the metalsurfaces in the well. Additionally, the treatment had the furtherbeneficial effect of removing sludge deposits from the pumpingequipment, and the flow lines leading away from the well. In the latterinstance, the treatment was at the ambient temperature and was far belowthe initial temperature of 200 R, such as 60-70 F. or even lower. Themodified cleaning solution which was produced upon contact of theinitial cleaning solution with the sludge and oil in the Well, waseffective for removing sludge even at the lower temperatures.

What is claimed is:

1. A method of removing paraffin-containing deposits on surfaces in oilwells comprising introducing lecithin into the interior of the well andinto intimate contact with the said deposits, introducing an aqueoussolution of alkali which contains suflicient alkali to saponify thelecithin into the interior of the well and into intimate contact withthe said deposits, the alkali being selected from the group consistingof alkali metal hydroxides, carbonates, phosphates and silicates, andthereafter introducing water into the interior of the well and flushingthe well therewith.

2. The method of claim 1 wherein the lecithin is in a hydrocarbonsolvent.

3. The method of claim 1 wherein a polyvalent metal silicate isintroduced into the interior of the well in the presence of thelecithin.

4. The method of claim 3 wherein the polyvalent metal silicate isselected from the group consisting of calcium silicate and magnesiumsilicate.

5. A method of preparing a cleaning composition comprising heating amixture comprising about 2-3 pounds of a micelle-forming water solublerosin acid soap, about 6-10 pounds of a water soluble alkali metalsilicate, about 30-150 grams of a water soluble alkaline earth metalsalt, about 1-3 pounds of lecithin, about 2-3 pounds of triglyceridevegetable oil, and about 2-4 pounds of an alkali selected from the groupconsisting of alkali metal hydroxides, carbonates and phosphates in anaqueous medium at an elevated temperature between about 80 C. and theboiling point until the mixture reacts and sets to a pasty mass uponcooling to normal room temperature.

6. The method of claim 5 wherein the mixture contains about 2-3 poundsof an alkali metal rosin soap as the micelle-forming soap, about 6-10pounds of an alkali metal metasilicate, about 2-3 pounds of vegetableoil, about 2-4 pounds of alkali metal hydroxide, about 6-10 pounds of avegetable oil partially saponified with an alkaline earth metalhydroxide, about 1-3 pounds of lecithin, about 3-6 gallons of ahydrocarbon solvent, about 2-6 pounds of an alcohol selected from thegroup consisting of cyclohexanol and methylcyclohexanol, about 11220-100 grams of magnesium sulfate, about 10-50 grams of calcium chlorideand about 6-10 gallons of water.

7. The cleaning composition prepared by the method of claim 5.

8. A method of removing solid paraflin-containing material depositedfrom crude petroleum on a surface in contact therewith comprisingintimately contacting the deposit of the said solid parafiin-containingmaterial with a cleaning composition prepared by the method of claim 5,and thereafter intimately contacting the deposit of the said solidparafiin-containing material with water.

9. A method of removing solid paraifin-containing material depositedfrom crude petroleum on a surface in contact therewith comprisingintimately contacting the deposit of the said solid paraflin-containingmaterial with a cleaning composition prepared by the method of claim 6,and thereafter intimately contacting the deposit of the said solidparafiin-containing material with water.

References Cited UNITED STATES PATENTS 1,513,371 10/1924 Campbell252-855 2,032,174 2/1936 Johnson 252-855 2,218,306 10/1940 Austerman166-38 2,580,765 1/1952 Hall et a1. 252-855 2,770,307 11/1956 Deerdofi166-41 2,805,200 9/1957 Lee et a1. 252-855 2,817,635 12/1957 Goldman etal 252-855 FOREIGN PATENTS 1,293 1856 Great Britain.

2,959 1872 Great Britain.

516,218 12/1939 Great Britain.

LEON D. ROSDOL, Primary Examiner.

ALBERT T. MEYERS, H. B. G'UYNN,

Assistant Examiners.

1. A METHOD OF REMOVING PARAFFIN-CONTAINING DEPOSITS ON SURFACES IN OILWELLS COMPRISING INTRODUCING LECITHIN INTO THE INTERIOR OF THE WELL ANDINTO INTIMATE CONTACT WITH THE SAID DEPOSITS, INTRODUCING AN AQUEOUSSOLUTION OF ALKALI WHICH CONTAIN SUFFICIENT ALKALI TO SAPONIFY THELECITHIN INTO THE INTERIOR OF THE WELL AND INTO INTIMATE CONTACT WITHTHE SAID DEPOSITS, THE ALKALI BEING SELECTED FROM THE GROUP CONSISTINGOF ALKALI METAL HYDROXIDES, CARBONATES, PHOSPHATES AND SILICATES, ANDTHEREAFTER INTRODUCING WATER INTO THE INTERIOR OF THE WELL AND FLUSHINGTHE WELL THEREWITH.